Toll-like receptors 2, 3, 4, 7, and 9 (TLR2/3/4/7/9)

Toll-like receptors (TLRs) 2, 3, 4, 7, and 9 are a subset of pattern recognition receptors (PRRs) that are essential components of the innate immune system, primarily expressed on antigen-presenting cells (APCs) such as dendritic cells and macrophages. These receptors detect specific pathogen-associated molecular patterns (PAMPs), including bacterial lipopolysaccharides (TLR4), lipoproteins (TLR2), double-stranded RNA (TLR3), single-stranded RNA (TLR7), and unmethylated CpG DNA (TLR9) (Source: UniProt). Upon activation, they initiate signaling cascades through adapter proteins like MyD88 or TRIF, resulting in the maturation of dendritic cells and the production of pro-inflammatory cytokines and interferons (Source: PubMed: 21115918). This activation is a critical bridge between innate and adaptive immunity, facilitating the priming of T-cell and B-cell responses. In clinical practice, these receptors are targeted by agonists to serve as vaccine adjuvants or to stimulate anti-tumor immunity in oncology (Source: NIH). However, dysregulated TLR signaling is also implicated in chronic inflammatory and autoimmune diseases, making them targets for both agonistic and antagonistic therapeutic strategies (Source: PubMed: 16751770). This target entry is technically a composite of five distinct receptors, each with unique structural and functional profiles.

Other names

TLR2TLR3TLR4TLR7TLR9Pattern Recognition ReceptorsPRRsCD282CD283CD284CD287CD289

Agonists bind to the leucine-rich repeat (LRR) domains of the receptors, inducing conformational changes that promote dimerization and recruitment of cytosolic adapter proteins MyD88 or TRIF. This initiates signaling cascades that activate NF-κB and IRF transcription factors, leading to the production of pro-inflammatory cytokines and Type I interferons (Source: PubMed: 16751770, UniProt).